The specific aims of this proposal are to study the process of cell division by combining the techniques of laser microbeam irradiation, light microscopy and electron microscopy. We propose to continue our studies on vertebrate cells in culture and to initiate some new studies on plant systems. Studies will be undertaken in which the centriolar region is irradiated with different laser wavelengths in combination with the treatment of light-sensitive compounds, such as acridine orange, BrdU, psoralens. The structure and function of the centriolar region will then be studied by time lapse analysis, electron microscope analysis and polarizing microscopy. Similar studies will be undertaken for kinetochores. Studies will also be undertaken involving laser microirradiation of spindle microtubules followed by behavioral, EM and polarizing microscopy. These studies are aimed at elucidating the mechanism of chromosome movements. A new series of studies is also proposed involving elucidation of the mechanism of cell division in the fungi. Another major goal of this proposal is the further development of the laser microbeam equipment.